THE NERVOUS SYSTEM 21 



gans are discharging impulses to motion with- 

 out having been subjected to any particular 

 sensory stimulation. These two classes of ac- 

 tivities are continually exhibited in our higher 

 nervous life and afford some of its most dif- 

 ficult problems. 



So far as our intellectual activities are con- 

 cerned, our sense organs may be said to be re- 

 ceiving incessantly notices of external changes 

 and to be transmitting these notices to the 

 central organs rather as information than as 

 incentives to action. From the eyes, the ears, 

 from the nose, the tongue, from the organs 

 of touch, from the cold and heat spots, 

 from the organs of pain and the deep-lying 

 muscle receptors, and from myriads of other 

 and unknown sensory mechanisms a steady 

 flow of impulses pours into the central organs. 

 The vast volume of this flood is of no spe- 

 cial service except in so far as it enables us, 

 partly consciously and partly unconsciously, 

 to adjust ourselves to the momentary state of 

 the environment. But certain currents in the 

 general flow influence us much more than the 

 rest and come to be more or less permanent 

 eddies in our mental stream. These eddies be- 

 gin to catch in early childhood, and as mem- 



